bug#52018: 28.0.60; Improve documentation for compilation-finish-functions

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: Thibault Polge <thibault@thb.lt>,  52018@debbugs.gnu.org
> Date: Wed, 24 Nov 2021 08:02:52 +0100
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> Thanks for the clarification. This makes sense, I'm just not sure how to
> >> act on this.  Would you rather drop this change or modify it to use more
> >> cautious language?  
> >
> > Not sure, actually.  Lars, WDYT?
> 
> The string that's passed in is a pretty free-form string, so I'm not
> sure what we could say about it in the manual that'd be meaningful.

So I guess we want to drop this patch, since the existing doc string
already says vaguely enough that the string describes how the process
finished.